Lipoprotein particle abnormalities and the impaired lipolysis in renal insufficiency

Lipoprotein particle abnormalities and the impaired lipolysis in renal insufficiency Background Increased concentrations of very low- (VLDL) and intermediate-density (IDL) lipoproteins in chronic renal failure (CRF) are thought to result from a defect(s) in degradation of plasma triglyceride (TG)-rich lipoproteins. The purpose of this study was to identify lipoprotein abnormalities associated with the reduced lipolytic rate constant, k 1 , of combined VLDL and IDL substrate from renal patients and asymptomatic controls. Methods The VLDL + IDL were isolated from 18 predialytic patients (CRF-I), 8 patients on hemodialysis (CRF-II) and 10 asymptomatic controls. The lipolytic rate constant (k 1 ) of VLDL + IDL was measured by an assay using bovine milk lipoprotein lipase and determination of TG before and after incubation by gas chromatography (GC). Neutral lipids were measured by GC and apolipoproteins by electroimmunoassays; the apolipoprotein-defined TG-rich lipoproteins including Lp-B:C, Lp-B:C:E and Lp-A-II:B:C:D:E were determined by immunoaffinity chromatography. Results The k 1 values of VLDL + IDL were significantly ( P -1 , respectively) than controls (0.0515min -1 ). The levels of apolipoproteins B, C-III and E, and TG-rich Lp-B:C, Lp-B:C:E and Lp-A-II:B:C:D:E particles normalized to 100mg TG per VLDL + IDL were significantly higher in both groups of CRF patients than in controls. All three TG-rich lipoproteins were characterized by significantly increased percent contents of free (FC) and esterified (CE) cholesterol and a decreased percentage of TG. The k 1 values of the combined CRF-I and CRF-II patient groups showed significant negative correlations ( P r = -0.81) and CE ( r = -0.63) and a positive correlation with TG ( r = 0.72). Among lipoprotein particles, only Lp-A-II:B:C:D:E levels showed a significant negative correlation with k 1 values ( r = -0.47, P Conclusions This study shows that the abnormal neutral lipid composition of all three TG-rich lipoprotein particles and increased concentrations of Lp-A-II:B:C:D:E particles represent the main factors affecting the in vitro lipolytic rates of VLDL + IDL substrate in both the CRF patients before dialysis and patients on hemodialysis.